- Speech impairment and hearing impairment reporting rates for children under 10 years of age were statistically increased at baseline, but not for the followups. Reporting rates decreased for all other age groups.
- Reporting rates for anemia and other blood disorders increased at all collection points, particularly for those aged less than 10 years and people aged 35 through 64 years.
- Stroke was reported in excess at each data collection period. The greatest increases were for females aged 10 through 54 years and males 25 through 44 years.
- Urinary tract disorders were reported at a higher rate for females in all age groups, and for males aged 10 through 25 years.
- Reported rates for liver problems were elevated or significantly higher for females aged 45 through 64 years; kidney problems were also reported in excess at baseline for females aged 55 through 64 years.
- Diabetes rates were higher for females aged 18 through 24 years and 45 through 54 years at all reporting periods; there was an overall increase at Followup 3.
- Skin rashes, eczema, and other skin allergies were reported at a higher rate at baseline and Followup 3; the two youngest age groups (less than 17 years) had the highest rates.
- hearing impairment (after age 25 years);
- asthma, emphysema, or chronic bronchitis;
- arthritis, rheumatism, or other joint disorders; and
- other respiratory allergies or problems, such as hay fever.
The use of company or product names is for identification only and does not constitute endorsement by the Agency for Toxic Substances and Disease Registry or the U.S. Department of Health and Human Services.
EXECUTIVE SUMMARY
This report provides an overview of the Agency for Toxic Substances and Disease Registry (ATSDR) Trichloroethylene (TCE) Subregistry Baseline and Followup activities, and the results of a comparison of TCE Subregistry reporting rates of health outcomes with national norms. The TCE Subregistry is one of four chemical-specific subregistries, along with the Benzene, Trichloroethane (TCA), and Dioxin Subregistries, that comprise the National Exposure Registry (NER). The NER is a database composed of names and other relevant information of persons with documented exposure to specific chemicals. The NER was created in response to a mandate given in the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (11). This mandate was reiterated in the Superfund Amendments and Reauthorization Act of 1986 (12).
The purpose of the NER is to assess long-term health consequences of long-term exposure to low levels of environmental contaminants (1). One of the goals to accomplish this purpose is to establish a database that will provide information needed to generate appropriate and valid hypotheses for future activities, such as epidemiologic studies. The NER is not a definitive study; cause and effect relationships cannot be established using only NER-based information. However, analysis of NER data can assist researchers in identifying health outcomes that warrant consideration for future studies or activities.
The data files for each chemical-specific subregistry were established at the time baseline data were collected, updated at each followup, and maintained by ATSDR on an ongoing basis. At baseline, information collected from each registrant included environmental data, demographic information, smoking and occupational history, and self-reported responses to 25 general health status questions. These same questions are asked at each followup. The first update (Followup 1) occurs 1 year after baseline, and subsequent followups occur biennially. At this time, there have been five followups at the Michigan and Indiana sites; four at the Illinois sites; three at the Pennsylvania site; and two at the Arizona site.
The TCE Subregistry Baseline data file includes information collected on 4,986 persons (4,652 living, 334 deceased) with documented environmental exposure to TCE, who had resided in 15 areas in 5 states (three sites in Michigan, four in Indiana, six in Illinois, one each in Pennsylvania and Arizona). TCE registrants were exposed through drinking water from TCE-contaminated private wells. To be eligible for the TCE Subregistry, persons had to have lived in one of the affected areas for more than 30 days and used the water at an address where the water supply (private wells) was contaminated with TCE. For eligible persons who were deceased at baseline or subsequent followups, death certificates were obtained and pertinent information abstracted. The participation rate for those eligible at baseline exceeded 98% at each site, and participation of approximately 89% of the registrants has been retained at each followup. Most loss of participation is due to inability to locate participants. Less than 2% of losses are because of refusal to participate.
The health-outcome rates in the TCE Subregistry Baseline, Followups 1 and 2 data (for all sites), and Followup 3 (for Illinois, Indiana, and Michigan) were compared with composite morbidity rates from the 1989–1994 National Health Interview Survey (NHIS), administered by the National Center for Health Statistics (NCHS). ATSDR has previously reported results of comparisons of TCE Subregistry reporting rates for most health outcomes with appropriate NHIS annual files; cancer reporting rates with data files from the National Cancer Institute's Surveillance, Epidemiology and End Results Program (SEER), mortality rates with national mortality data from the NCHS, and TCE Subregistry intrafile comparisons between exposure groups based on level and duration of exposure (2, 3).
Morbidity data analyses indicated TCE Subregistry registrants had an increased reporting rate for several health outcomes, most of which were consistent across data collection points. However, because of small numbers, for some time periods a change of 1 in the number of reports or in the sample size changed the level of statistical significance. The following statistically significant increases (p≤.01 significance level) were found:
When interpreting statistical results, and planning future activities based on these results, certain limitations of the TCE Subregistry data files must be kept in mind. For instance, a bias in reporting rates could exist because (1) registrants were more aware of their TCE exposure, (2) had been advised of the potential effect on their health, and/or (3) might have sought medical care more often than the general population. To moderate this potential bias, TCE Subregistry data were collected with the restriction that a health care provider had to have either told the registrant they had, or treated them for, the condition. Statistically significant deficits for the TCE population were found for the following health conditions:
However, these conditions are often self-diagnosed and medical care is not always sought for them. Consequently, reporting rates would be affected by the restriction requiring confirmation by a health care provider, and this is reflected in the results.
It is noteworthy that some questions in the two data-collection instruments used for this analysis were worded differently, making direct comparisons of the reported rates more difficult to interpret. Also, there is a possibility that, given the large number of comparisons used in the analyses, there might be some false positive findings. These limitations and restrictions are discussed further in this report.
In the original Baseline report (2), the environmental data collected were explored for potential dose-response relationships. The limited environmental data available (usually, the results of one or two well water sample tests) dictates that the results of these analyses be interpreted with caution. (Note: In order to further explore the environmental levels of exposure experienced by the registrants, ATSDR used the historical data in a modeling project; unfortunately this project did not produce new insights useful for dose-response calculations.) The most striking finding from the limited statistical analyses carried out was the significant elevation in stroke risk with increased maximum TCE exposure levels. The results also suggested other associations, such as respiratory diseases with cumulative exposure to TCE and other chemicals, and hearing problems with length of exposure. It should be noted that the outcomes stroke and hearing impairment were also significantly higher in the morbidity outcome comparisons with NHIS.
Although the findings of this report do not identify a causal relationship between TCE exposure and adverse health effects, they do reinforce the need to continue ongoing followup of registrants. ATSDR is investigating two health outcomes (diabetes and anemia) identified previously as needing further study. Additional information will be collected for TCE registrants who respond positively to questions about these two conditions. The NER questionnaires have been altered to more closely align the questions with the appropriate questions in the NHIS questionnaire.
Another goal of the National Exposure Registry is to inform registrants of all current information related to their exposures. A TCE Registrant Report, written for the general public and summarizing the findings of this technical report, was mailed to each registrant in June 1999. ATSDR conducted public availability sessions at each site in June 1999 to discuss the findings described in this report.